Method and apparatus for chemical monitoring

ABSTRACT

The present invention relates to monitoring chemicals in a process chamber using a spectrometer having a plasma generator, based on patterns over time of chemical consumption. The relevant patterns may include a change in consumption, reaching a consumption plateau, absence of consumption, or presence of consumption. In some embodiments, advancing to a next step in forming structures on the workpiece depends on the pattern of consumption meeting a process criteria. In other embodiments, a processing time standard is established, based on analysis of the relevant patterns. Yet other embodiments relate to controlling work on a workpiece, based on analysis of the relevant patterns. The invention may be either a process or a device including logic and resources to carry out a process.

RELATED APPLICATIONS

This application claims the benefit of provisional applications filed onJul. 25, 2003, Application No. 60/490,084, entitled “Method andApparatus for Chemical Monitoring of Atomic Layer Deposition (ALD)Processes” by inventor Herbert E. Litvak; Application No. 60/490,372,entitled “Method and Apparatus for Optical Emission Leak Detection inVacuum Systems” by inventors Herbert E. Litvak and Gary B. Powell; andApplication No. 60/490,113, entitled “Method and Apparatus forMonitoring Chemical Utilization/Efficiency in Chemical ProcessingEquipment” by inventors Herbert E. Litvak and Gary B. Powell, whichprovisional applications are hereby incorporated by reference.

This application is also related to and incorporates by reference theInternational Application No. PCT/US01/44585 entitled “Method and DeviceUtilizing Plasma Source for Real-Time Gas Sampling” filed in the U.S.Receiving Office on Nov. 29, 2001 designating the U.S. and othercountries and published in English, which claims the benefit of U.S.application Ser. No. 10/038,090 filed by inventors Richard L. Hazard andGary Powell on Oct. 29, 2001 and Ser. No. 09/726,195 filed by ApplicantLightwind Corporation and inventor Gary Powell on Nov. 29, 2000; andincorporates by reference U.S. application Ser. No. 09/631,271 entitled“Inductively Coupled Plasma Spectrometer for Process Diagnostics andControl” filed by inventor Gary Powell on Aug. 2, 2000. Various patentshave issued in this family and continuations are pending.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialthat is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to monitoring chemicals in a processchamber using a spectrometer having a plasma generator, based onpatterns over time of chemical consumption. The relevant patterns mayinclude a change in consumption, reaching a consumption plateau, absenceof consumption, or presence of consumption. In some embodiments,advancing to a next step in forming structures on the workpiece dependson the pattern of consumption meeting a process criteria. In otherembodiments, a processing time standard is established, based onanalysis of the relevant patterns. Yet other embodiments relate tocontrolling work on a workpiece, based on analysis of the relevantpatterns. The invention may be either a process or a device includinglogic and resources to carry out a process.

2. Description of Related Art

Semiconductor manufacturing has adopted various telemetry techniquesutilizing mass spectrometry or spectrographic analysis to improve thecleaning, conditioning or operation of reaction chambers in which avariety of reactions take place, such as deposition, cleaning, etching,implantation, ashing, etc. Telemetry techniques help operators monitorprocesses that take place on a microscopic level inside a closed chamberthat often is sensitive to any form of outside radiation. One technologysometimes used is monitoring a plasma reaction chamber to view radiationemitted by process plasma. Another technology is to use a massspectrometer to analyze residual gases. More recently, these inventorshave begun using a spectrometer having a plasma generator to analyzeprocess gases.

One area of process analysis interest is the efficiency of a chemicalreactor and its ability to transform feed gases (which themselves maynot be reactive) into reactive species, which can undergo and/or producedesired chemical changes. In a plasma etcher, the action of the plasmamay convert stable, otherwise unreactive feed gases into reactivechemical atoms and radicals that then remove surface materials on thesubstrate to be etched. An example is the plasma breakdown of unreactiveCF4 into highly reactive F atoms, which remove Si, SiO2, and/or Si3N4from the surface of silicon wafers. In plasma-assisted deposition, theplasma may assist in breakdown of a precursor such as TaCl5 into Taatoms, which are deposited onto a semiconductor surface.

Chemical conversion efficiency, sometimes called “chemical utilization”is rarely measured, because of the difficulty of making proper chemicalmeasurements.

Another area of interest is monitoring of atomic layer deposition (ALD),also known as alternating layer deposition. ALD is a method ofdepositing thin films of materials onto substrates, including thefabrication of semiconductor electronic devices. As opposed to moreconventional deposition methods (e.g. Chemical Vapor Deposition—CVD, orthermal film growth), in which the important steps of film formation(e.g. adsorption of precursor species onto the substrate, followed bychemical reaction steps of the adsorbed film) occur simultaneously, ALDbreaks the steps into separate, discrete processing steps, in order toachieve preferred film properties. These properties may include stepcoverage, across-wafer uniformity, and reduced film contamination. TheALD process can be carried out at lower substrate temperatures thanother deposition processes, which is useful generally and, inparticular, in temperature-sensitive processes.

A related area of interest is detection of air leaks into a processchamber. One process for leak detection is described in “Air LeakEvaluation of a Production Dry Etcher by Means of Optical EmissionSpectroscopy”, F. Ciaovacco, S. Alba, F. Somboli, G. Fazio, AEC/APCSymposium XIV, 2002. The technique described requires a plasma in theprocess chamber to cause emission of light with a wavelength attributedto CN. The CN is formed by chemical combination in the plasma of carbonatoms from a flow of carbon-containing feed gas, e.g. CF4, which hasbeen admitted to the reaction chamber for this purpose and N atoms fromN2 molecules in the air leak. The described technique is applied to aplasma reaction chamber, using a window to observe emissions from theplasma. The technique described does not work with non-plasma processchambers where there is no ionization.

Given the anticipated desire for improved process control, a process andrelated device that addresses any or all of the areas of interest aboveand/or related areas of interest would be well received. A workabletelemetry process would create an opportunity to improve manufacturingprocess performance.

SUMMARY OF THE INVENTION

The present invention relates to monitoring chemicals in a processchamber using a spectrometer having a plasma generator, based onpatterns over time of chemical consumption. The relevant patterns mayinclude a change in consumption, reaching a consumption plateau, absenceof consumption, or presence of consumption. In some embodiments,advancing to a next step in forming structures on the workpiece dependson the pattern of consumption meeting a process criteria. In otherembodiments, a processing time standard is established, based onanalysis of the relevant patterns. Yet other embodiments relate tocontrolling work on a workpiece, based on analysis of the relevantpatterns. The invention may be either a process or a device includinglogic and resources to carry out a process. Particular aspects of thepresent invention are described in the claims, specification anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

A schematic block diagram of a monitoring system is shown in FIG. 1.

FIG. 2 illustrates one type of signal behavior that can be obtained.

FIG. 3 shows an expected process signal for a TaCl5 and H precursor ALDprocess.

Determination of a final steady state value is illustrated by FIGS. 4-5.FIG. 4 is a generalized representation of an optical emission signalfrom an ALD process step, similar to FIG. 3. FIG. 5 represents themathematical first derivative of FIG. 4.

FIG. 6 indicates how the system leak rate can be obtained by comparisonof signals with and without calibrated leaks open.

DETAILED DESCRIPTION

The following detailed description is made with reference to theFigures. Preferred embodiments are described to illustrate the presentinvention, not to limit its scope, which is defined by the claims. Thoseof ordinary skill in the art will recognize a variety of equivalentvariations on the description that follows.

A variety of spectrometers having a plasma generator may be used withthe methods described below. A spectrometer system in this disclosureincludes a plasma generator and an array of detectors, such as aspectrometer. An optical detector monitors concentrations of gases inthe plasma generator, by means of their plasma-excited characteristicoptical emission signals. The plasma generator includes an excitationchamber and external electrodes. The chamber may be made of a variety ofmaterials that are compatible with a range of processes being monitored.Etch reactions typically require corrosive gases and significantlyaffect excitation chamber material choices. A quartz chamber, forinstance, is unlikely to be compatible with etch processes containingfluorine, because quartz is etched by fluorine. Ceramics, such as highpurity aluminum oxide (sometimes called alumina) or sapphire, aresuitable for monitoring fluorine etch processes. Ceramics havingsubstantial silicon content are less desirable, because fluorine orchlorine can remove the silicon. Boron carbide and nitride are otherceramics that resist fluorine and chlorine and might be used as astructural or coating material. Zirconia is another ceramic that mayhave the desired characteristics. Generally, any ceramic-like materialmay be used that is compatible with sustained exposure to fluorine orother halogen-based reactive chemical gases. Preferably, theceramic-like material should be compatible with both fluorine andchlorine etching.

An excitation chamber preferably has a small volume, such as 40-70 cubiccentimeters, as power requirements are low per volume and it ispreferred to use a low power level to sustain a plasma discharge. Lowpower requirements eliminate the need for water or forced air cooling,which may be used in alternate embodiments. Low power requirements tendto extend the lifetime of components. Typical power requirements dependon the process that the system is monitoring. Power levels of 15 to 75watts are suitable for a wide range of monitoring tasks. Power levels of50 to 75 watts are suitable for monitoring a higher-pressure process,above 1 torr, such as a stripping process. Power levels of 20 to 50watts are suitable for monitoring etch and deposition processes. Powerlevels as low as 5 to 20 watts could be used if the plasma excitationchamber were reduced in size to a volume of approximately 5 to 15 cubiccentimeters. A smaller chamber in the volume range of 1 to 5 cubiccentimeters could be used although gas transport at pressures below 150millitorr may reduce its responsiveness. It is desirable for the powersetting of an excitation chamber to be software controlled and adjusted,manually or automatically, to modify the light emission from the plasma.The software can evaluate the light emission at a chosen wavelength orset of wavelengths during a chosen stage of operation and adjust thepower to generate the desired light emission. Alternatively, recipes canbe developed based on experience that includes particular power levelsfor particular circumstances where the software can automatically stepthrough sequences that match the state or condition of the processoperation. The power adjustment impacts the overall instrumentsensitivity. This provides a second way to increase system sensitivityto spectral emissions.

The plasma generator can use a range of RF frequencies for excitation.One useful frequency is 13.56 MHz±1 MHz, which is an unlicensedoperating band. Other frequencies from 1 MHz to 900 MHz are also useful.At the low end of the range, frequencies of 1 MHz or greater requireless driving voltage to generate a plasma. At the upper end, theresponse of the ions and electrons to the excitation frequency changestheir behavior. Within the overall range, other frequencies areavailable while those that do not require licensing are preferable. Useof the predominate 13.56 MHz drive frequency generates a familiarspectral output. Other frequencies that also may be used include 27 and40 MHz. Excitation frequencies below 1 MHz can cause increased erosion(sputtering) of electrode materials and therefore reduced sourcelifetimes. Frequencies at or above 1 MHz are more efficiently coupledthrough dielectrics such as quartz or ceramics. External electrodes canbe problematic to implement below 1 MHz with ceramic or anodizedaluminum excitation chambers, for instance. A requirement for plasmaspowered by external electrodes is efficient power transfer through thedielectric. Many applications use gases that chemically attack sourcematerials or walls. In using materials that are chemically durable,excitation frequencies above 1 MHz couple power more effectively intothe plasma. Frequencies above 900 MHz can be harder to ignite. Apreferred range of operating frequencies is about 13 to about 40 MHz.

The source can operate from below 5 millitorr to above 5 torr withoutrequiring pressure control or additional pumping while requiring minimalpower input.

The window material through which the spectra are transmitted is made ofsapphire because of its resistance to most process chemistry. Asecondary issue is the deposition of sampled gas byproduct on thesapphire window. When the plasma generator for the spectrometer has thecapability of having reducing or other reactive gases added directly toit, those gases may be ionized and act in a manner to keep the spectraltransmission window clean. This secondary gas input allows the use ofthe gases without contamination or effect on the actual process chamber.

A variety of detector arrays can be used with this invention, asdescribed more fully in the disclosures incorporated herein byreference. A useful configuration of detectors and a diffraction gratingincludes spacing the detectors in relation to the diffracted light sothe detectors are responsive to band widths sufficiently narrow that aplurality of detectors are responsive to a single peak in an emissionspectrum. A prepackaged device capable of focusing detectors on wavebands of 1.23 nm FWHM bandwidth is a Sony ILX511 device. In analternative embodiment, a Sony device with a USB interface can be used.Either Sony device includes a 2,048 detector CCD array and a diffractiongrating. Individual elements are 12.5 mm×200 mm. The well depth of anindividual element at 600 nm is 160,000 photons. The estimatedsensitivity may be expressed as 86 photons/count, 2.9×10-17 joule/count,or 2.9×10-17 watts/count for 1-second integration. Its effective rangeis 200-1000 nm and its integration time may be 3 ms with a 1 MHz A/Dcard or 4 ms with a 500 kHz A/D card. The Sony IXL511 device can beconfigured with a grating that diffracts radiation in the 200 to 850 nmspectrum. A slit of 25 mm is typical, with 10, 50 and 100 mm slitsavailable. Various combinations of groove density, fiber diameter andslit width can be selected for additional sensitivity or a widerspectral range. Optics suitable to UV radiation in the 200-350 nm rangeare used. Order sorting is accomplished with a single-piece,multi-bandpass detector coating for applications in the 200-850 nmspectrum. Detector enhancements that increase UV sensitivity aresusceptible to false signals at shorter wavelengths. A coating is usedto reduce the effects of wavelengths that are second or third harmonicsof the signal of interest. A scan time for collecting and convertingdata from the array elements is 20 milliseconds or less. In acost-sensitive application, a more modest array having 1024 or 512detectors can be used. In an even more cost-sensitive application, aplurality of detectors can be used, either with a diffraction grating orwith filters that effectively tune the respective detectors to specificwave bands or wavelengths.

A processor, logic and resources with various capabilities are coupledto the spectrometer. In one embodiment, the logic and resourcesrecognize the start of individual process steps, analyze the relevantoptical emission signals from the optical detector in terms ofconcentrations of chemical species, and optionally communicate thisinformation to a user or the processing tool. This system also could beconfigured to control the plasma generator, the optical detector, andrelevant peripheral components. Suitable interface hardware and softwareallow the spectrometer with a plasma generator to communicate with auser or the process tool.

A schematic block diagram of a monitoring system is shown in FIG. 1. Aprocess chamber 111 is shown, without the detail of feeds or processesconducted in the chamber. Two different configurations of the plasmagenerator 112 a, 112 b are shown in FIG. 1. The solid lines show theconfiguration 112 b for process monitoring downstream of the processchamber. The process chamber is connected to an exhaust or vacuum pump122 via an exhaust or vacuum line 121. The spectrometer with a plasmagenerator is branched 126 off the exhaust line and exhaust gas diffusesinto the ICP source 112 b. This configuration may be advantageous if gaspressures in the process chamber are too high for acceptable operationof the plasma generator. A variation on this configuration, which is notillustrated, flows at least part of the gas through the ICP source, ofrelying on diffusion. A pressure reducer may be used with this flowthrough variation. Alternatively, under appropriate pressure conditions,the plasma generator can be mounted directly onto the process chamber,as shown in dashed lines 112 a. Chamber gases diffuse into the source.Also illustrated are a power supply 131 for the source 112, amulti-channel emission spectrometer 124, a data acquisition and controlcomputer 134 and various couplings. An optical fiber 123 couples thesource 112 with the spectrometer 124. An interface 125 couples thespectrometer 124 with the computer 134. Another interface 132 couplesthe power supply 131 with the computer 134. A third interface 133, suchas a communications link, may couple the tool 111 with the computer 134.This link can include any number of standard communication protocolscommonly in use in the semiconductor equipment industry, e.g., analog,digital logic level (TTL), SECS-GEM, TCP/IP, or other.

Chemical Utilization

One application of monitoring chemicals in a process chamber ismonitoring of chemical utilization. A process that applies to this andother areas of interest may include monitoring gas in the processchamber with a spectrometer having a plasma generator, calibrating themonitoring, and introducing the first chemical and forming or patterninga layer on a workpiece, while observing a pattern over time ofconsumption of a first chemical based on the intensity of the spectralpeaks. Calibration of the monitoring may include flowing a knownquantity or concentration of the first chemical into the process chamberand observing an intensity of one or more spectral peaks of a secondchemical, the spectral peaks corresponding to consumption of the firstchemical. Generally, calibration may establish run-time processmonitoring standards or process time standards, as two ways of applyingthe results of analysis to process control. Such a process, optionally,also may apply to the layer formed or patterned as a layer of one ormore semiconductor device structures. The process further may includeadvancing to a next step in forming the structures on the workpieceafter the pattern of consumption over time of the first chemical meets aprocess criteria. Various process criteria are described below.

Chemical utilization may focus on current chemical utilization, changingchemical utilization, patterns of utilization or cumulative utilization.Calibration of detector signals in terms of chemical concentrations canbe obtained for stable species, by flowing a known concentration of thespecies of interest (e.g. CF4) into the chemical monitor, and observingthe strength of its associated characteristic optical emission signal(e.g. 262 nm CF2 emissions are characteristic of CF4 concentrations). Acalibration coefficient can be calculated, e.g., as the ratio ofobserved signal to known chemical concentration. Alternatively, moresophisticated methods can be employed, such as using several differentknown species concentrations, and calculating the calibrationcoefficient as a function, such as a linear slope, of the signal vs.concentration curve.

FIG. 2 illustrates one type of signal behavior that can be obtained. Inthis figure, the optical emission signal strength is plotted on thevertical axis 210. The signal strength may be proportional to chemicalconcentration. The horizontal axis 220 represents time. Two curves aredepicted, 232-233-234 and 235-236-237. A reactant species, such as CF4,is introduced into a process chamber. During a first time interval, tothe left of 231, the concentration of the first species is relativelysteady, with variations inherent in measurement or in the process. Whenthe stable CF4 is used in an etching process, plasma processing convertsit into a reactive species, CF2. A spectrometer with a plasma generatorcan readily measure emissions from plasma of the reactive species CF2.In a plasma etching chamber, the consumption of CF2 depends on thesurface being etched. Removing a patterned resist layer, for instance,may produce a first relatively stable concentration 232 of CF2. As theresist layer is exhausted in patterned areas, for instance exposingsilicon, the consumption of CF2 changes, as indicated by the downwardslope 233, to the right of 231. Due to variations in resist layerthickness, gas flow, or other reasons, the change in CF2 concentrationis not instantaneous. After a time, CF2 begins reacting with theunderlying layer producing a second relatively steady pattern ofconsumption 234. Chemical utilization monitoring can be applied to theinitial steady-state concentration 232, the changing concentration thatcorresponds to a change in the reaction within the process chamber 233or the second steady-state concentration 234. In parallel with changedCF2 concentration, silicon-fluorine compounds, such as SiF2 and SiF4change in concentration. Before etching breaks through the resist layer,the initial steady state concentration of silicon reaction products hasa relatively low concentration 235. As the consumption of CF4 changes,so does the production of reaction products 236. In a typical case, theproduction of reaction products reaches a second relatively stablepattern corresponding to consumption of the reactant species being fedinto the process chamber.

A simple measure of chemical utilization (“CU”) can be calculated fromthe data of FIG. 2, such asCU=(Final Steady-state CF2 Signal−Initial Steady-state CF2Signal)/(Initial Steady-state CF2 Signal), orCU=(Final Steady-state SiF2 Signal−Initial Steady-state SiF2Signal)/(Final Steady-state CF2 Signal−Initial Steady-state CF2 Signal).

Either of these definitions (or several others that can be devised)provides a useful measure of processing tool efficiency, which can betracked over time and utilized in a statistical (or other) processcontrol scheme. In the case of stable species, e.g. CF4, CU can becalculated in terms of absolute concentrations, provided the requiredcalibration work has been done. For transient species, e.g. F atoms, thecalculated CU will be relative, but still extremely useful in a processcontrol scheme. Such a process control scheme can greatly improvereactor productivity and reduce the amount of misprocessed material, byquickly flagging “out of spec” reactor efficiency.

The chemical monitor described here is well adapted to give real-timereadouts of chemical concentrations, both before and immediately afterplasma turn-on in the chemical reactor, thus providing for calculationof CU in near real time for every wafer passing through the plasmareactor.

An example of implementation on a plasma-processing chamber is shown.This technique is, however, independent of that requirement.Spectrographic characterization can rely on relative peak heights ofidentified species; however, those same peaks and ratio of peak heightsmay exhibit a unique behavior with respect to the ionization sourceused. Comparison of spectra from different process chambers may belimited because of the different ionization properties of thosechambers. Among spectrometers, use of a consistent plasma generatorreduces the difference in ionization properties. Any semiconductormanufacturing process that has a gas ionization source may be acandidate for the application of this technique.

Other chemical processes, such as thermally enabled deposition also canbe characterized by application in this way. For thermally enableddeposition, chemical utilization might be monitored while making changesin the operating temperature of the system. It is understood thatchanges in operating temperature may also cause changes in any reactionrate and particularly in thermally enabled deposition. A corollary tomonitoring the effect of changed operating temperatures is use ofchemical utilization to estimate the temperature of a vessel. When aprocess has been characterized, reaction rate or chemical depletion canbe correlated to those variables, such as operating temperature, whichaffect the reaction rate. In chemical reactions that are not plasmaenhanced, the reaction rate is many times thermally driven, so a changein reaction rate corresponds to a change in temperature.

Several variations on chemical vapor deposition are listed byEncyclopedia.TheFreeDictionary.com, which would be known to one ofordinary skill in the art. “Chemical Vapor Deposition (CVD) is achemical process for depositing thin films of various materials. In atypical CVD process the substrate is exposed to one or more volatileprecursors, which react and/or decompose on the substrate surface toproduce the desired deposit. Frequently, volatile byproducts are alsoproduced, which are removed by gas flow through the reaction chamber.[¶] CVD is widely used in the semiconductor industry, as part of thesemiconductor device fabrication process, to deposit various filmsincluding: polycrystalline, amorphous, and epitaxial silicon, SiO2,silicon germanium, tungsten, silicon nitride, silicon oxynitride,titanium nitride, and various high-k dielectrics. [¶] A number of formsof CVD are in wide use and are frequently referenced in the literature.”

Metal-Organic CVD (MOCVD) processes use metal-organic precursors, suchas Tantalum Ethoxide, Ta(OC2H5)5, to create TaO, Terta Dimethyl aminoTitanium (or TDMAT) and, in turn, to create TiN.

Plasma Enhanced CVD (PECVD) processes utilize a plasma to enhancechemical reaction rates of the precursors. PECVD processing allowsdeposition at lower temperatures, which is often useful in themanufacture of semiconductors.

Remote Plasma Enhanced CVD (RPECVD) is similar to PECVD, except that thewafer substrate is not directly in the plasma discharge region. Removingthe wafer from the plasma region allows processing temperaturesapproaching room temperature.

Rapid Thermal CVD (RTCVD) processes use heating lamps or other methodsto rapidly heat the wafer substrate. Heating only the substrate ratherthan the gas or chamber walls helps reduce unwanted gas phase(gas-to-gas contact) reactions that can lead to particle formation.

Atmospheric Pressure CVD (APCVD) processes proceed at atmosphericpressure.

Low Pressure CVD (LPCVD) processes take place at sub atmosphericpressures. Reduced pressures tend to reduce unwanted gas phase reactionsand improve film uniformity across the wafer. Most modern CVD processesare either LPCVD or UHVCVD. Ultra-High Vacuum CVD (UHVCVD) processesproceed at very low pressures, typically in the range of a few to ahundred millitorr.

Atomic Layer CVD (ALCVD) is a process in which two complementaryprecursors (e.g. Al(CH3)3 and H2O) are alternatively introduced into thereaction chamber. Typically, one of the precursors will adsorb onto thesubstrate surface in molecular layers, but cannot completely decomposewithout the second precursor. The precursor adsorbs until it covers thesurface and attenuates atomic forces that cause the adsorption. Furtherprogress in layer deposition cannot occur until the second precursor isintroduced. Thus, the film thickness is controlled by the number ofprecursor cycles rather than the deposition time, as is the case forconventional CVD processes. In theory, ALCVD allows for extremelyprecise control of film thickness and uniformity.

CVD precursor materials fall into a number of categories such as:

-   -   Halides—TiCl4, TaCl5, WF6, etc    -   Hydrides—SiH4, GeH4, AlH3(NMe3)2, NH3, etc    -   Metal Organic Compounds—    -   Metal Alkyls—AlMe3, Ti(CH2tBu)4, etc    -   Metal Alkoxides—Ti(OiPr)4, etc    -   Metal Dialylamides—Ti(NMe2)4, etc    -   Metal Diketonates—Cu(acac)2, etc    -   Metal Carbonyls—Ni(CO)4, etc    -   Others—include a range of other metal organic compounds,        complexes and ligands.

Application of chemical utilization monitoring may permitcharacterization of various interesting points in production processes.For instance, changed chemical utilization may signal changes in theetch or deposition rate of materials due to different surface areas thatetch. Changes in utilization may result from changes in hardwareconfiguration, for instance replacement of materials that react to agreater or lesser extent with the process chemistry. Consumption ratesof equipment components that react chemically to the plasma or chemicalprocess (for example, quartz is etched in the presence of fluorine) canbe monitored. Build up of materials deposited in a chamber, eitherdeliberately or as reaction byproducts (for example, polymers thatcontribute to particulate generation) can be monitored.

Atomic Layer Deposition

A typical cycle of ALD steps would include: 1) pumping out or purgingthe system to remove unwanted or residual gases; 2) admit a precursorgas, such as TaCl5 in the case of Ta deposition, allowing it enoughcontact time with the substrate to form a monolayer of adsorbed TaCl5;3) pumping out or purging excess TaCl5; 4) contacting the precursor witha reactive gas, such as atomic H from the dissociation of H2 or NH3,allowing it enough contact time with the adsorbed TaCl5 to react awaythe Cl atoms (forming gaseous HCl), thus leaving a monolayer of Ta; and5) pumping out or purging excess H (plus undisassociated H2 or NH3) andthe HCl reaction product. In some processes, little or no distinctpurging may be required, as the flow of one gas into the process chambernaturally displaces the prior gas.

Since the amount of film deposition in any one ALD process cycle isextremely low (typically <˜1A), many cycles (sometimes hundreds orthousands) must be repeated, in order to achieve usable film thickness.Even if a process cycle requires only a few seconds, the necessity ofrepeating it so many times produces a very slow overall process (˜1 hourbeing typical). Thus wafer throughput may become a hurdle to integratingALD into a semiconductor device manufacturing flow.

Decreasing overall ALD process time involves decreasing times ofindividual steps. One may decrease the contact time of the gases withthe substrate in steps 2) and 4), above, and/or to reduce the pump outor purge times in steps 1), 3), and 5). Chemical utilization monitoringmay be able to detect patterns of adsorption. For example, in step 2),after TaCl5 is introduced, when the TaCl5 concentration reaches asteady-state (or other pre-selected) value, it would be safe to assumethat no more adsorption of TaCl5 onto the surface is occurring, andfurther contact time would have no benefit. Similarly, applied to thechemical reaction in step 4), when the concentration of HCl falls to asteady-state baseline (or other pre-selected) value, it would be safe toconclude that further contact time would have no benefit to filmformation, and the process step can be terminated. Similarconsiderations hold for the pump-out or purge steps: when theconcentration of the species to be removed has fallen to a baseline (orother pre-selected) value, there is no point in continuing the purge.Alternatively, when the purge is intended to reduce undesired reactionsbetween gasses, as opposed to gas-to-adsorbed layer reactions, reactionproducts of gas-to-gas contact could be monitored and patterns ofreaction product concentration monitored to determine how short a purgecan be applied without excessive gas-to-gas contact reactions. Becauseso many process cycles are performed in any one deposition, the abilityto adjust step times in real-time could have a significant impact onoverall process time.

Implemented in a device, logic and resources would be combined withother elements of the spectrometer with a plasma gas source, the logicand resources adapted to recognize the start of the individual processsteps, analyze the relevant optical emission signals from the opticaldetector to recognize “end of process step” signature (e.g. the signalor signal slope achieving a pre-selected value), and communicate thisinformation to a user or the ALD processing tool. A second function ofthe computer would, optionally, be to control the plasma generator, theoptical detector, and relevant peripheral components.

FIG. 3 shows an expected process signal for the TaCl5 and H ALD processdescribed above. The vertical axis 310 represents the HCL opticalomissions signal, which is proportional to HCL concentration. Thehorizontal axis 320 tracks time. After adsorption of TaCl5, H isintroduced into the process chamber. Prior to or at the beginning of thereaction between the precursors 331, the HCL signal is relatively low,following a first steady pattern. Between the process start 331 and thehigh point of HCL concentration 332, the HCL signal strength trendsupward. The reaction proceeds, producing to a relatively steadyconcentration pattern 332. Then, the HCL concentration drops to a finalsteady state value 333, which indicates that all of the absorbed TaCl5has reacted with H, so there is no more Cl to liberate and combine withH. Process termination would be signaled when the HCl signal reaches asteady-state value (indicating cessation of evolution of HCl from theprocess step).

Determination of a final steady state value 333 is illustrated by FIGS.4-5. FIG. 4 is a generalized representation of an optical emissionsignal from an ALD process step, similar to FIG. 3. FIG. 5 representsthe mathematical first derivative of FIG. 4. Steady-state behavior ofchemical concentration in an ALD process step implies that theconcentration of the species of interest is no longer changing. Sinceoptical emission signals are proportional to chemical concentrations,steady-state behavior can be inferred from an optical emission signalfrom the appropriate chemical species that is no longer changing. Thisis illustrated by FIG. 4. The vertical axis 410 indicates opticalemissions signal intensity. The horizontal axis 420 tracks time. Abaseline 431 provides a background reference. A signal 436-437-438changes over time. During a first time interval 436, for instance beforeH begins reacting with adsorbed TaCl5, the signal is at a baseline. Asin FIG. 3, the signal, for instance HCL emissions, rises to a plateau437, and then drops. A final steady state concentration of HCl 438 isdetected, which is expected to be above the original baseline. Thisfinal steady state concentration may be flat or slowly diminishing.

Mathematically, it follows that the first derivative of the opticalemission signal (i.e. the signal slope) is zero for some period of time(i.e. not simply instantaneously). Thus, steady-state behavior can beinferred by examination of the first derivative of the optical emissionsignal shown in FIG. 5, for a persistent zero slope or a near-zeroslope, taking into account noise sources. In FIG. 5, the vertical axis510 is a positive or negative value indicating the first derivative ofthe signal in FIG. 4. That is, a near-zero value of the first derivative541, 543, 545 corresponds to a flat segment of the signal 436, 437, 438.A positive value of the first derivative 542 corresponds to a risingportion of the signal, as between 436 and 437. A negative value 544corresponds to a descending portion of the signal, as between 437 and438. In this figure, a tolerance band 532 is indicated for detecting anear-zero slope. A threshold for negative slope detection 533 also isindicated.

To avoid confusing the steady-state signal behavior at the start of theprocess step with the desired steady-state behavior at the end of theprocess step, a mathematical criterion can be imposed, such as apersistent, short-term negative first derivative be detected (e.g.,lasting for at least some number k data points, k typically being ˜2-10data points over some time that depends on the sampling rate) before azero or near-zero first derivative is recognized. This condition isindicated as “Threshold for Negative Slope Detection” in FIG. 3 b. Thecondition can only be met for signals that are decreasing in intensity,i.e. nearing the end of a process step similar to the one in FIG. 3 a.Once the “Negative Slope Criterion” has been met, a persistent near-zeroslope is a satisfactory indication of a steady-state condition. This“Near-Zero Slope Criterion” can be expressed mathematically as apersistent first derivative signal within a Tolerance Band, asillustrated in FIG. 3 b. The persistence can be expressed mathematicallyas n consecutive first derivative data points (n typically ˜2-10), whosevalue lies within the Tolerance Band (assuming the “Negative SlopeCriterion” has already been met.)

Described stepwise, detection of steady-state behavior may include:

-   -   1) Acquiring optical emission data points.    -   2) Calculating the mathematical first derivative of that data        point (requires that at least two data points have been        acquired).    -   3) Examining the first derivative relative to the “Negative        Slope Criterion” (NSC).    -   4) If the NSC has not been met, repeat from 1).    -   5) If the NSC has been met, acquire a new data point, calculate        the first derivative, and test if the “Near-Zero Slope        Criterion” (NZSC) has been met.    -   6) If the NZSC has been met, signal “Stop Process” (or similar        output) to the ALD processing tool.    -   7) If the NZSC has not been met, repeat from 5).

An additional mathematical criterion can be imposed on the data at thepoint that the “Near-Zero Slope Criterion” has been met (=“Zero SlopePoint”), viz. to compare the optical emission signal at that point withthe original baseline signal level of the data (calculated, e.g., as theaverage of several data points just before or just after the start ofthe process step). If the former is appreciably above the later, thismay indicate an accumulation of some impurity or contaminant in theprocess chamber, and steps may need to be taken to correct thesituation. A suitable warning signal could be displayed on a userinterface screen and/or communicated to the ALD process tool over thecommunication link.

Precursor Sufficiency

As described above, precursors may be combined to form a useful layer ona substrate, as part of a structure of the semiconductor device. Inaddition, precursors may be combined to form a useful etchant, forinstance by adsorption of water vapor followed by introduction offluorine gas. In some processes, there are many points of potentialfailure in delivery of precursors to the process chamber. The potentialfailure points depend on how the precursor is delivered. Three typicalmodes of delivering precursors are: (a) bubbling a carrier gas through aliquid precursor; (b) atomizing a liquid precursor; or (c) heating andvaporizing a precursor, either from a solid or liquid form. To evaluatethe sufficiency of precursor concentrations or quantities in thechamber, an optical emission line of interest can be selected, typicallycorresponding to one of the decomposition products of converting theprecursor to a plasma in the plasma generator. The spectrometer withplasma generator is calibrated using a controlled concentration orquantity of the precursor in the reaction chamber, under conditionssimulating the desired process. When the process operates, thespectrometer with plasma generator can compare an optical emissionsignal to the calibrated standard signal. An operator or the processtool can be advised if too little precursor has reached the processchamber. In some processes, the sufficiency of the precursor in theprocess chamber can be evaluated before the reaction proceeds, eitherbefore energizing a plasma or before introducing an additionalprecursor. In other processes, many layers accumulate, allowing anopportunity for intervention before the layer is spoiled.

Leak Detection

The method for detection of leaks and other vacuum system contaminantsincludes several general steps that may be combined or sub combined invarious ways. These steps could be performed manually or automaticallyin a leak detection sequence. The sequence could be started by amaintenance operator, an engineer or by an appropriate message over acommunications link from the vacuum system (as part of its internalmaintenance procedures). Following is the sequence of events.

1. Determine that the vacuum system is in the desired condition. Thatcondition could be an idle or not processing state. It could also beduring an inactive process step when there is gas flow but no ionizationof gasses in the process chamber. Initiation of a test of system vacuumintegrity could be manual or automatic, by a message from the hostsystem or detection of a particular operating mode. Preferably, the testoccurs when there is a determination that the vacuum system has reacheda steady-state condition, indicated by constant or relatively steadyoutput of optical emission signals. The vacuum system should be in amode in which gas pressure and flows are in steady state, such as“processing”, “idle”, etc. when the leak detection steps are executed.Unsteady gas pressure or flows would complicate leak ratequantification.

2. Acquire emission spectra from the ICP source at wavelengthsindicative of an air leak (e.g. 387 nm for CN, a reaction product ofleaky nitrogen and a carbon source. These signals constitute“Background” signal levels, SBkg(1).

3. Admit a controlled amount of leak detection gas (e.g., CF4 or SF6),and once again acquire emission spectral signals S(1) from the ICPsource at wavelengths indicative of an air leak. By leak detection gas,we mean a gas that reacts with a leak when ionized. This leak detectiongas can be introduced to the process chamber or downstream, for instancein the vacuum line 121 (see FIG. 1) or in a vacuum connection 126between the vacuum line and the plasma generator. Calculate the signaldifferences, Snet(1)=S(1)−SBkg(1).

4. Open a first calibrated leak, wait for the system to equilibrate,again acquire emission spectral signals S(1), and compute signaldifferences Snet(1) with the first calibrated leak open.

5. Repeat with one or more additional calibrated leaks in the system.

6. Close calibrated leaks and stop flow of the leak detection gas intothe vacuum system.

7. Compute system air leak rate. FIG. 6 indicates how the system leakrate can be obtained by comparison of signals with and without thecalibrated leaks open. In this figure, the vertical axis 610 is theoptical emission signal. The horizontal axis 620 corresponds to a leakrate. A regression line 630 is calculated to correlate the opticalomissions signal with the leak rate. It is anticipated that a linear fitwill result. At point 631, a signal is recorded corresponding to a firstcalibrated leak. At point 633, a signal level is recorded correspondingto a second calibrated leak. Optionally, at point 634, a signal level isrecorded with both first and second calibrated leaks. As a furtheroption, additional points, such as point 632 can be recorded,corresponding to additional calibrated leaks. From the regression line630, an intercept 641 can be calculated. At some intercept value, aresidual vacuum system leak is apparent, because the intercept value isabove 642 a baseline optical omissions signal 643 for a system with noleaks. This baseline signal may be calculated, for instance, with theplasma generator not energized, to take into account stray current andother factors impacting the spectrometer.

If signals from multiple wavelengths 1 are obtained, a separate leakrate can be calculated for each wavelength utilized. Standardstatistical methods can then be used to calculate a “best estimate” leakrate. Another approach would be to calculate a signal-to-noise ratio(SNR) at each of the wavelengths being tracked, and use only thewavelengths of highest SNR for leak rate determination. (This lattermethod builds in protection against unanticipated spectral interferencesthat may arise in the vacuum system.)

8. Report computed leak rate to a user at the computer monitor and tothe vacuum system. Optionally, the computed leak rate can be compared toone or more tolerance values, to determine suitability of the system forfurther operation. “System OK”, “System Warning” or “System Abort”signals can optionally be sent to the vacuum system based uponcomparison of the computed leak rate with tolerance values.

9. Signal “Procedure End” state to the vacuum system.

While this calibration process has been described in the context of leakdetection, the same process for correlation of particular flows throughthe process chamber with optical emission signals at the spectrometerwith plasma generator can be applied generally, either with or withoutregression through the data points.

We have observed that optical leak detection can also be detected byattenuation of certain chemical signals (e.g. F atom emission at 703.7nm from leak detection gases such as SF6), in addition to the formationof new signals (e.g. CN.) When SF6 is used as a leak detection gas, aleak attenuates a signal associated with the SF6. Thus the signalSnet(1) may be a negative number. This attenuation mode may be moresensitive for leak detection in some environments than formation of anew signal.

Use of the downstream source allows leak detection to be performed in anon-plasma system or under conditions when the etch plasma is notactive, e.g. during equipment “maintenance” or “idle” states, and insystems which do not have plasma generation capability, or the abilityto optically monitor a plasma. Thus, leak detection can be performedvirtually any time the system is under vacuum, not just when etching isbeing performed. In addition, leak detection may be more sensitive (e.g.have a lower detection limit) when the system is in idle or maintenancemode than in etch mode, because of spectral interferences from etchreactant or product gases during etch. Using this approach, baseline gasbreakdown and energy levels can be characterized and used as references.Real time or near real time processes can be compared to this referenceand changes in the process that generate byproduct or consume reactantcan be compared to the reference. Because emission spectra can becorrelated to concentration changes, reaction rates/depletion rates canalso calculated as they occur. Additional Embodiments

The present invention may be practiced as a method or device adapted topractice the method. In one environment, the methods disclosed are usedto form structures of semiconductor devices on the surface of a wafer.The methods disclosed also can be used to form a layer on a workpiece,such as a layer that is part of a structure of a semiconductor device ona wafer. The invention can be viewed from the perspectives ofmanufacturing a device, of operating manufacturing equipment, ofcontrolling a manufacturing process, or of responding to gaseous inputswith analytical or control information. Software that embodies aspectsof the invention may be an article of manufacture, such as mediaimpressed with logic to carry out any of the disclosed methods. Also asan article of manufacture, software that embodies aspects of theinvention may be practiced as the data stream carrying logic adapted tocarry out the disclosed methods.

A first method embodiment provides a method of monitoring chemicalutilization within a process chamber. This method includes monitoringgas in the process chamber with a spectrometer having a plasma generatorthat is gaseously coupled to the process chamber. The gaseous couplingmay be directly to the process chamber, as through a port, or to anexhaust from the process chamber. The gaseous coupling may operate bydiffusion into or by gaseous flow through the plasma generator. Types ofprocess chambers that are mentioned in some detail above include plasmaetching, non-plasma dry etching, and many types of deposition chambers.Other reaction chambers to which the disclosed methods might be appliedinclude cleaning, implantation and ashing chambers. Application of themethods disclosed is not meant to be limited to these types ofsemiconductor manufacturing process chambers, or to semiconductormanufacturing. The method further includes calibrating the monitoring byflowing a known quantity or concentration of the first chemical into theprocess chamber and observing an intensity of one or more spectral peaksof the second chemical, the spectral peaks corresponding to consumptionof the first chemical. The first chemical may be consumed bydecomposition or by reaction with other chemicals. Typically, multipledetectors of narrow bandwidth will fit under the spectral peaks of thesecond chemical. With experience, these inventors have learned, contraryto their prior teachings, that stoichiometric analysis using a known,nonreactive gas, such as argon, is not necessary in order to calibrate aspectrometer having a plasma generator. Even across machines, it nowappears that standards can be established using a spectrometer having aplasma generator based on standard process chamber operating conditions,without undue experimentation. This method embodiment further includesintroducing the first chemical and forming or patterning a layer on aworkpiece, while observing a pattern over time of consumption of thefirst chemical based on the intensity of the spectral peaks. The firstchemical may be introduced to the reaction chamber, between the reactionchamber and the plasma generator or, in the case of leak detection,outside the reaction chamber. Introducing the first chemical and formingor patterning a layer on a workpiece may proceed simultaneously or insequence. In most processes, the intensity the spectral peaks will beobserved while forming or patterning the layer. In some processes, forinstance, for leak detection or precursor sufficiency evaluation, thespectral peaks may be observed and evaluated prior to forming orpatterning the layer, so as to avoid spoiling a workpiece or as to allowcorrection of or compensation for a problem. A pattern over time ofconsumption is observed, rather than just an instantaneous spectralintensity. Over time, the dynamics of the process can be monitored.Rates of processes and changes in rates of processes can be observed.Monitoring can be applied to one or more gases flowing through thechamber at a predetermined rate or it can be applied to one or moregases dumped into the chamber in a predetermined quantity orconcentration. That is, a continuous flow, plug flow or batch reactordesign can be monitored.

An additional, optional aspect of this method takes into account thatthe layer formed or patterned in the introducing step described above isa layer of one or more semiconductor device structures on the workpiece.This aspect further includes advancing to the next step in forming thestructures on the workpiece after a pattern of consumption over time ofthe first chemical meets a process criteria. The process criteriadepends on how the method is being applied, for instance to chemicalmonitoring, atomic layer deposition or leak detection.

One process criteria is a cumulative amount of the first chemicalconsumed over time.

Another process criteria applies to a precursor that mixes with one ormore other gases. This process criteria is that a sufficient amount ofthe precursor is present in the gas mixture to form the layer. Thepattern of consumption over time may begin before the precursor isintroduced and may reflect adsorption of the precursor onto theworkpiece. In this instance, the precursor will be consumed in theplasma generator of the spectrometer, by decomposition. Alternatively,the pattern of consumption over time may follow adsorption of anotherprecursor onto the workpiece, so the consumption involves combining twoprecursors. In a reaction chamber with ionizing energy, for instance,this process criteria may be evaluated prior to energizing a plasma inthe process chamber.

Two further process criteria look at a changing rate of consumptioncorresponding to a change in one or more reactions in the processchamber. One looks for an indication that the consumption rate has begunto change and the other looks for an indication that the consumptionrate has changed and stabilized. In terms of a curve, the first looksfor curve segment that is relatively steady or flat followed by a curvesegment that rises or falls. The second looks for a curve segment thatis rising or falling, followed by a curve segment that is relativelysteady or flat. In some instances, the process criteria may involve afirst relatively steady pattern of consumption, followed by a changingrate of consumption, followed by a second steady rate of consumption.

Several process criteria may be applied to leak detection. One leakdetection criteria uses the first chemical that is a leak detection gasthat reacts with a leak gas in the plasma generator to produce thesecond chemical. Applying this process criteria, the calibrating step ofthe first method embodiment further includes flowing a calibrated leakgas into the process chamber. The process criteria for advancing to anext step in forming structures of the device is substantial absence ofthe leak gas. Details of calibration and analysis for one embodiment aregiven above. Optionally, introducing the first chemical precedes theforming or patterning step and observing consumption over time coincideswith introducing the first chemical. For some processes, the leakdetection process criteria may be evaluated prior to energizing a plasmain the processing chamber.

Several aspects of the first leak detection criteria optionally may beapplied. The leak detection gas may be a carbon-fluorine compound, suchas CF4. It may be a sulfur-fluorine compound, such as SF6.

The second leak detection criteria uses the first chemical that is aleak detection gas, introduced between the process chamber at the plasmagenerator that reacts with a leak gas in the plasma generator to producethe second chemical. Applying the second detection criteria avoids anyneed to introduce the leak detection gas into the process chamber. Likethe first leak detection criteria, applying this criteria, thecalibrating step further includes flowing a calibrated leak gas into theplasma generator and the process criteria is substantial absence of theleak gas. Again, this process criteria may be evaluated prior toenergizing a plasma in the process chamber that is used for the formingor patterning.

The third leak detection criteria uses a first chemical that is a leaktracing gas, that is, a chemical that leaks into the process. This firstchemical reacts with other gases to produce the second chemical. Forinstance, a leak tracing gas that includes a carbon compound may reactswith nitrogen that also leaks into the chamber or which is ambient andthe chamber to produce a carbon-nitrogen compound such as CN. The leaktracing gas should be a material that is substantially lacking from theambient atmosphere surrounding the process chamber, which is introducedto the ambient atmosphere surrounding the process chamber to locate oneor more leaks. This method may pinpoint a leak into a chamber operatingat a sub atmospheric pressure.

Another approach to chemical monitoring and process criteria is usingthe chemical monitoring to set a process criteria, which is a productiontime standard; that is, to set a standard time interval during which aproduction step proceeds. One way of setting a process criteria,according to this approach, includes applying the introducing andforming or patterning step one or more times to test workpieces andestablishing a production time standard for the forming or patterning ofthe layer, based on a cumulative amount of the first chemical consumedover time. It further includes forming or patterning a layer of one ormore structures on a production workpiece using the production timestandard, wherein the process criteria for advancing to the next step isthe production time standard. This production time standard approachrecognizes that the staff of a fabrication facility will be familiar andcomfortable with production recipes that include production timestandards for various production steps. An experienced and crediblestaff unit may use consumption monitoring to set production timestandards that are then applied in the manufacturing of structures andsemiconductor devices.

A second way of setting a process criteria, according to this approach,includes applying the introducing and forming or patterning step one ormore times to test workpieces and establishing a production timestandard for the forming or patterning of the layer, based on a changingrate of consumption for the first chemical corresponding to a reactionin the process chamber after a relatively steady pattern of consumption.It further includes forming or patterning a layer of one or morestructures on a production workpiece using the production time standardwherein the process criteria for advancing to the next step is theproduction time standard.

Another way of setting a process criteria includes applying theintroducing and forming or patterning step one or more times to testworkpieces and establishing a production time standard for the formingor patterning of the layer, based on a second relatively steady patternof consumption of the first chemical, which follows both a firstrelatively steady pattern of consumption and a changing rate ofconsumption that corresponds to a reaction change in the processchamber. It further includes forming or patterning a layer of one ormore structures on a production workpiece using the production timestandard, wherein the process criteria for advancing to the next step isthe production time standard.

Several alternative aspects and features of the first method embodimentdo not depend on advancing to a next step in forming the structures onthe workpiece after the pattern of consumption over time meets a processcriteria. The several alternative aspects and features that follow willsound familiar, but they depend directly from the first methodembodiment identified above.

According to one aspect of the first method embodiment, the gas couplingbetween the process chamber and the spectrometer having a plasmagenerator includes directing exhaust gas from an exhaust of the processchamber to the plasma generator. According to an alternative aspect, thegaseous coupling includes diffusion from a port on the process chamberinto the plasma generator.

Coordinated with observing the pattern of consumption over time, themethod further may include controlling work on the workpiece based on acumulative amount of the first chemical consumed over time. Or, it mayfurther include, when the first chemical is a precursor that mixes withone or more gases, controlling work on the workpiece based on asufficient amount of precursor in the gas mixture for forming orpatterning the layer. When the first chemical is a precursor, thesufficiency of the precursor may be evaluated prior to energizing aplasma in the process chamber that is used for the forming orpatterning.

Coordinated with observing the pattern of consumption over time, themethod alternatively may further include controlling work on theworkpiece based on a consumption rate curve. The consumption rate curvemay indicate a changing rate of consumption of the first chemicalcorresponding to a change in one or more reactions in the processchamber, after a relatively steady rate of consumption. The consumptionrate curve may indicate a relatively steady rate of consumption of thefirst chemical, and after a changing rate of consumption correspondingto a change in one or more reactions in the process chamber. Or, theconsumption rate curve may indicate a second relatively steady patternof consumption of the first chemical, after a first relatively steadypattern of consumption followed by a changing rate of consumptioncorresponding to change in one or more reactions.

For leak detection, coordinated with observing the pattern ofconsumption over time, one option uses the first chemical that is a leakdetection gas that reacts with the leak gas in the plasma generator toproduce the second chemical. Following this option, the calibrating stepfurther includes flowing a calibrated leak gas into the process chamberand the method further includes controlling work on the workpiece basedon a substantial absence of the leak gas. One aspect of this option mayinvolve introducing the first chemical before the forming or patterningand the observing over time is coincident with introducing the firstchemical. Another aspect is that the substantial absence of leak gas maybe evaluated prior to energizing a plasma in the process chamber that isused for forming or patterning.

An alternative option for leak detection introduces the first chemicalthat is a leak detection gas between the process chamber and the plasmagenerator. Other features and aspects of this option may be as describedfor the preceding option.

A different option for leak detection uses the first chemical that is aleak tracing gas. Following this option, the leak tracing gas reactswith other gases to produce the second chemical and controlling work onthe workpiece is based on a substantial absence of the leak tracing gas.The leak tracing gas may be a material substantially lacking from anambient atmosphere surrounding the process chamber, which is introducedto the ambient atmosphere surrounding the process chamber to locate oneor more leaks.

Production time standards may be set depending directly from the firstmethod embodiment. The general approach involves applying theintroducing and forming or patterning step one or more times to testworkpieces and establishing a production time standard, then forming orpatterning a layer of one or more structures on a production workpieceusing the production time standard. There are at least three options forsetting the production time standard. One is basing the standard on acumulative amount of the first chemical consumed over time. Another isbasing the standard on a changing rate of consumption of the firstchemical corresponding to a reaction change in the process chamber,after a relatively steady pattern of consumption. The third is basingthe standard on a second relatively steady pattern of consumption of thefirst chemical, and after a first relatively steady pattern ofconsumption followed by a changing rate of consumption of the firstchemical corresponding to changing reaction.

While the embodiments above generally include either proceeding to thenext step in forming a device or controlling work on the workpiece, themethods disclosed may usefully be practiced without either proceeding tothe next step or controlling work.

Several additional embodiments are described in the provisionalapplications identified above and incorporated by reference. A furthermethod embodiment is a method of detecting a steady chemical conditionwithin a process chamber. This method includes introducing a chemicalmixture into the process chamber and monitoring the chemical mixture ina device outside the process chamber, utilizing a spectrometer withplasma generator, and detecting at least one emission signal. Thisembodiment further includes observing the detected emission signal anddetecting that at least one component of the chemical mixture was beingconsumed by reaction and observing the detected initial signal anddetecting that the consumption of the component was substantiallyreduced.

Another method embodiment of detecting a steady chemical conditionwithin a process chamber includes introducing a chemical mixture intothe process chamber and monitoring the chemical mixture in a deviceoutside the process chamber, utilizing a spectrometer having a plasmagenerator and detecting at least one emission signal. This embodimentfurther includes observing the detected emission signal and detectingthat a rate of consumption of a component of the chemical mixture hasconsequently changed.

Several more leak detection embodiments can be described. One beginswith a process chamber in an initial state and includes monitoring a gascomposition in a device outside the process chamber, utilizing aspectrometer having a plasma generator and detecting at least oneemission signal “A”. This embodiment further includes providing amonitor gas that is reactive with a leak gas and detecting at least oneemission signal “B”. It further includes introducing a calibrated leakgas into the process chamber and detecting at least one emission signal“C”. The emission signals “A”, “B” and “C” are then used to calculate aleak rate of infiltration of the leak gas into the process chamber. Oneoption for this embodiment is introducing the calibrated leak gas to thereaction chamber through at least two leak ports. Another aspect is thatat least two of the emission signals use the same optical emissionwavelengths.

Another leak detection embodiment is a method of detecting a leak into aprocess chamber, the process chamber beginning in an initial state. Thisembodiment includes monitoring a gas composition in a device outside theprocess chamber, utilizing a spectrometer having a plasma generator. Itfurther includes providing a monitor substance positioned in the deviceoutside the process chamber that is reactive with the leak gas anddetecting at least one initial emission signal. The monitor substancemay be a gas or a solid, such as a block of carbon or activatedcharcoal. It may be placed in or near the plasma generator. Thisembodiment further includes introducing a calibrated leak gas into theprocess chamber and detecting at least one calibrated emission signaland calculating a rate of infiltration of the leak gas into the processchamber using the initial and calibrated emission signals. One optionfor this embodiment is introducing the calibrated leak gas to thereaction chamber through at least two leak ports.

Another leak detection embodiment is a method of detecting a leak into aprocess chamber, the process chamber beginning in an initial state. Thisembodiment includes providing a device outside the process chamber,utilizing a spectrometer having a plasma generator and a monitorsubstance that is reactive with leak gas. It further includesestablishing a baseline emission signal with the process chamber in anacceptable state and monitoring a gas composition in the device outsidethe process chamber to detect a change in the baseline emission signalproduced by reaction of the monitor substance with the leak gas. Oneoption for this embodiment is that the change from the baseline may bedetected prior to energizing a plasma in the process chamber.

One chemical utilization embodiment includes introducing a consumablechemical into the process chamber and monitoring the consumable chemicalin a device outside the process chamber, utilizing a spectrometer havinga plasma generator and detecting at least one ignition signal. Thisembodiment further includes observing the detected emission signal anddetecting at least one proxy for the consumed chemical. It furtherincludes integrating over time consumption of the consumed chemical.

A second chemical utilization embodiment, like the first, includesintroducing a consumable chemical into the process chamber andmonitoring the consumable chemical in a device outside the processchamber, utilizing a spectrometer having a plasma generator anddetecting at least one emission signal. Unlike the first, it includesobserving the detected emission signal and detecting that a rate ofconsumption of at least one proxy for the chemical mixture has changed.

A monitor device embodiment includes a plasma generator external to andgaseously coupled to the process chamber, a spectrometer includingdetectors optically coupled to a plasma generator, and a deviceelectronically coupled to the spectrometer including detectors, thedevice including logic and resources adapted to carry out any of themethods described above, including embodiments, aspects, options andfeatures of those methods in various combinations.

While the present invention is disclosed by reference to the preferredembodiments and examples detailed above, it is understood that theseexamples are intended in an illustrative rather than in a limitingsense. It is contemplated that modifications and combinations willreadily occur to those skilled in the art, which modifications andcombinations will be within the spirit of the invention and the scope ofthe following claims.

1. A method of monitoring chemical utilization within a process chamber,including: monitoring gas in the process chamber with a spectrometerhaving a plasma generator that is gaseously coupled to the processchamber; calibrating the monitoring by flowing a known quantity orconcentration of a first chemical into the process chamber and observingan intensity of one or more spectral peaks of a second chemical, thespectral peaks corresponding to consumption of the first chemical; andintroducing the first chemical and forming or patterning a layer on aworkpiece, while observing a pattern over time of consumption of thefirst chemical based on the intensity of the spectral peaks.
 2. Themethod of claim 1, wherein the layer formed or patterned in theintroducing step is a layer of one or more semiconductor devicestructures; and further including advancing to a next step in formingthe structures on the workpiece after the pattern of consumption overtime of the first chemical meets a process criteria.
 3. The method ofclaim 2, wherein the process criteria is a cumulative amount of thefirst chemical consumed over time.
 4. The method of claim 2, wherein thefirst chemical is a precursor that mixes with one or more other gasses,and the process criteria corresponds to a sufficient amount of theprecursor in the gas mixture for the forming of the layer.
 5. The methodof claim 2, wherein the first chemical is a liquid precursor, whichmixes with one or more other gasses, and the process criteriacorresponds to a sufficient amount of the precursor in the gas mixturefor the patterning of the layer.
 6. The method of claim 4, wherein theprocess criteria is evaluated prior to energizing a plasma in theprocess chamber that is used for the forming or patterning.
 7. Themethod of claim 2, wherein the process criteria is a changing rate ofconsumption of the first chemical corresponding to a change in one ormore reactions in the process chamber, after a relatively steady patternof consumption.
 8. The method of claim 2, wherein the process criteriais a second relatively steady pattern of consumption of the firstchemical, after a first relatively steady pattern of consumptionfollowed by a changing rate of consumption of the first chemicalcorresponding to a change in one or more reactions in the processchamber.
 9. The method of claim 2, wherein the first chemical is a leakdetection gas that reacts with a leak gas in the plasma generator toproduce the second chemical; the calibrating step further includesflowing a calibrated leak gas into the process chamber; and the processcriteria is substantial absence of the leak gas.
 10. The method of claim9, wherein: the introducing of the first chemical precedes the formingand patterning; and the observing over time coincides with introducingthe first chemical.
 11. The method of claim 9, wherein the processcriteria is evaluated prior to energizing a plasma in the processchamber that is used for the forming or patterning.
 12. The method ofclaim 9, wherein the leak detection gas is a carbon-fluorine compound.13. The method of claim 9, wherein leak detection gas is CF4.
 14. Themethod of claim 9, wherein the leak detection gas is a sulfur-fluorinecompound.
 15. The method of claim 9, wherein leak detection gas is SF6.16. The method of claim 2, wherein the first chemical is a leakdetection gas that is introduced between the process chamber and theplasma generator and reacts with a leak gas in the plasma generator toproduce the second chemical; the calibrating further includes flowing acalibrated leak gas into the plasma generator, and the process criteriais substantial absence of the leak gas.
 17. The method of claim 16,wherein the process criteria is evaluated prior to energizing a plasmain the process chamber that is used for the forming or patterning. 18.The method of claim 2, wherein the first chemical is a leak tracing gasthat reacts with other gases to produce the second chemical; and theprocess criteria is substantial absence of the leak tracing gas.
 19. Themethod of claim 18, wherein the leak tracing gas is a materialsubstantially lacking from an ambient atmosphere surrounding the processchamber, which is introduced to the ambient atmosphere surrounding theprocess chamber to locate one or more leaks.
 20. The method of claim 19,wherein the leak tracing gas includes a carbon compound.
 21. The methodof claim 2, further including: applying the introducing and forming orpatterning step one or more times to test workpieces and establishing aproduction time standard for the forming or patterning of the layer,based on a cumulative amount of the first chemical consumed over time;and forming or patterning a layer of one or more structures on aproduction workpiece using the production time standard, wherein theprocess criteria for advancing to the next step is the production timestandard.
 22. The method of claim 2, further including: applying theintroducing and forming or patterning step one or more times to testworkpieces and establishing a production time standard for the formingor patterning of the layer, based on a changing rate of consumption ofthe first chemical corresponding to a reaction change in the processchamber after a relatively steady pattern of consumption; and forming orpatterning a layer of one or more structures on a production workpieceusing the production time standard, wherein the process criteria foradvancing to the next step is the production time standard.
 23. Themethod of claim 2, further including: applying the introducing andforming or patterning step one or more times to test workpieces andestablishing a production time standard for the forming or patterning ofthe layer, based on a second relatively steady pattern of consumption ofthe first chemical, after a first relatively steady pattern ofconsumption followed by a changing rate of consumption of the firstchemical corresponding to a reaction change in the process chamber; andforming or patterning a layer of one or more structures on a productionworkpiece using the production time standard, wherein the processcriteria for advancing to the next step is the production time standard.24. The method of claim 1, wherein the gaseous coupling between theprocess chamber and the spectrometer having a plasma generator includesdirecting exhaust gas from an exhaust of the process chamber to theplasma generator.
 25. The method of claim 1, wherein the gaseouscoupling between the process chamber and the spectrometer having aplasma generator includes diffusion from a port on the process chamberinto the plasma generator.
 26. The method of claim 1, further includingcontrolling work on the workpiece based on a cumulative amount of thefirst chemical consumed over time.
 27. The method of claim 1, whereinthe first chemical is a liquid precursor, which mixes with one or moreother gasses and further including controlling work on the workpiecebased on a sufficient amount of the precursor in the gas mixture for theforming of the layer.
 28. The method of claim 1, wherein the firstchemical is a precursor that mixes with one or more other gasses andfurther including controlling work on the workpiece based on asufficient amount of the precursor in the gas mixture for the patterningof the layer.
 29. The method of claim 28, wherein the sufficiency of theprecursor is evaluated prior to energizing a plasma in the processchamber that is used for the forming or patterning.
 30. The method ofclaim 1, further including controlling work on the workpiece based on achanging rate of consumption of the first chemical corresponding to achange in one or more reactions in the process chamber, after arelatively steady pattern of consumption.
 31. The method of claim 1,further including controlling work on the workpiece based on a secondrelatively steady pattern of consumption of the first chemical, after afirst relatively steady pattern of consumption followed by a changingrate of consumption of the first chemical corresponding to a change inone or more reactions in the process chamber.
 32. The method of claim 1,wherein the first chemical is a leak detection gas that reacts with aleak gas in the plasma generator to produce the second chemical and thecalibrating step further includes flowing a calibrated leak gas into theprocess chamber, and further including controlling work on the workpiecebased on a substantial absence of the leak gas.
 33. The method of claim32, wherein: the introducing of the first chemical precedes the formingand patterning; and the observing over time coincides with introducingthe first chemical.
 34. The method of claim 32, wherein the substantialabsence of the leak gas is evaluated prior to energizing a plasma in theprocess chamber that is used for the forming or patterning.
 35. Themethod of claim 1, wherein the first chemical is a leak detection gasthat is introduced between the process chamber and the plasma generatorand reacts with a leak gas in the plasma generator to produce the secondchemical and the calibrating further includes flowing a calibrated leakgas into the plasma generator; further including controlling work on theworkpiece based on a substantial absence of the leak gas.
 36. The methodof claim 35, wherein the substantial absence of the leak gas isevaluated prior to energizing a plasma in the process chamber that isused for the forming or patterning.
 37. The method of claim 35, whereinthe first chemical is a leak tracing gas that reacts with other gases toproduce the second chemical; further including controlling work on theworkpiece based on a substantial absence of the leak tracing gas. 38.The method of claim 37, wherein the leak tracing gas is a materialsubstantially lacking from an ambient atmosphere surrounding the processchamber, which is introduced to the ambient atmosphere surrounding theprocess chamber to locate one or more leaks.
 39. The method of claim 1,further including: applying the introducing and forming or patterningstep one or more times to test workpieces and establishing a productiontime standard for the forming or patterning of the layer, based on acumulative amount of the first chemical consumed over time; and formingor patterning a layer of one or more structures on a productionworkpiece using the production time standard.
 40. The method of claim 1,further including: applying the introducing and forming or patterningstep one or more times to test workpieces and establishing a productiontime standard for the forming or patterning of the layer, based on achanging rate of consumption of the first chemical corresponding to areaction change in the process chamber after a relatively steady patternof consumption; and forming or patterning a layer of one or morestructures on a production workpiece using the production time standard.41. The method of claim 1, further including: applying the introducingand forming or patterning step one or more times to a test workpiece andestablishing a production time standard for the forming or patterning ofthe layer, based on a second relatively steady pattern of consumption ofthe first chemical, after a first relatively steady pattern ofconsumption followed by a changing rate of consumption of the firstchemical corresponding to a reaction change in the process chamber; andforming or patterning a layer of one or more structures on a productionworkpiece using the production time standard.
 42. A monitor of chemicalutilization within a process chamber, including: a plasma generatorexternal to and gaseously coupled to the process chamber; a spectrometerincluding detectors optically coupled to the plasma generator; a deviceelectronically coupled to the spectrometer including detectors, thedevice including logic and resources adapted to, monitor gas in theprocess chamber using the spectrometer including detectors by observingan intensity of one or more spectral peaks; calibrate the monitoring,responsive to flowing a known quantity or concentration of a firstchemical into the process chamber, by observing an intensity of one ormore spectral peaks of a second chemical, the spectral peakscorresponding to consumption of the first chemical; and observe apattern over time of consumption of the first chemical based on theintensity of the spectral peaks, responsive to introducing the firstchemical and forming or patterning a layer on a workpiece.
 43. Themonitor of claim 42, wherein the layer formed or patterned in theintroducing step is a layer of one or more semiconductor devicestructures; and the logic and resources are further adapted to advanceto a next step in forming the structures on the workpiece after thepattern of consumption over time of the first chemical meets a processcriteria.
 44. The monitor of claim 42, wherein the logic and resourcesare further adapted to control work on the workpiece responsive tochanges in the pattern over time of consumption of the first chemical.